1. Field of the Invention
The present invention relates to a roughness measuring method and apparatus, more specifically to ones which are capable of precisely measuring a surface roughness of a workpiece, on which processed surfaces with different roughnesses are formed.
2. Description of the Related Art
A surface roughness measuring apparatus is used for inspecting finished surface of a processed workpiece. In general, inspecting standard values are indicated in a drawing which shows instructions for processing a workpiece. The inspection reference values are parameters to be evaluated (Ra: arithmetrical mean roughness, Rz: ten point mean roughness, Sm: mean spacing of profile irregularities) and an allowable limit of the parameter values (roughness) to be evaluated. The surface roughness of the workpiece is measured in accordance with the inspecting standard values.
In fact, there are often cases where plural processed surfaces with different roughnesses are formed on the same plane of the workpiece. In a conventional manner, each roughness is preliminarily measured and a measurement starting point and a measurement length are set for each surface, then an evaluation value of each surface is obtained.
However, the conventional roughness measuring method and apparatus preliminarily measure a roughness of each plane and set the measurement starting point and the measurement length for each plane before a formal measurement; thus a measuring process takes much steps.